Maximum likelihood detector algorithms are developed for the matrix of transmitted symbols in a multiuser system in which the received signal is the sum of K cochannel continuous phase modulated (CPM) signals and additive white Gaussian noise. We illustrate that the maximum likelihood matrix detector, which provides optimum detector performance, consists of K sets of front-end matched filters followed by a Viterbi algorithm. We also derive two reduced complexity receivers, demonstrating through simulation that they perform within 1-2 dB of the optimal while substantially reducing complexity. The paper demonstrates how performance can be traded off against complexity, giving particular attention to cochannel Gaussian minimum shift keyed (GMSK) signals.
Index Terms-Cochannel interference, Continuous Phase Modulation (CPM), interference suppression, Maximum Likelihood Sequence Estimation (MLSE), multiuser detection.
SUMMARYA successive interference cancellation (SIC) algorithm is developed for the interception of signals transmitted on a CDMA forward link. The system is modelled after the IS-95 standard but the results are also applicable to other CDMA systems such as the wideband CDMA (W-CDMA) and IS-2000 standards. In realistic systems, the different forward link channels are de-orthogonalised, leading to performance degradation in conventional matched filter (CMF)-type receivers. Simulation results indicate that the proposed SIC receiver ameliorates the detrimental effects of de-orthogonalisation, interference and multipath, exhibiting significant gains in traffic capacity over the capacity of a CMF. The numerical simulations also show that the proposed receiver is relatively insensitive to system imperfections. The techniques developed in this paper can be used for interception, surveillance, reconnaissance or monitoring of CDMA signals; to relax the strict requirements on power control; and to improve the capacity of CDMA systems.
In this paper, we evaluate the performance of several channel coding schemes for a weakly coherent optical communications system that employs binary Frequency-ShiftKeying. For the detection of signals, a double-filtering receiver structure is considered. Our numerical results, computed for BCH codes, Reed-Solomon codes, convolutional codes and a concatenated code, show that coding can provide a very economical solution for greatly improving the performance of such a system and for making it widely tolerant to laser phase noise.
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